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P105 Lecture #26 visuals

P105 Lecture #26 visuals. 18 March 2013. Anatomy of the Human Vocal Apparatus. Illustration from E.J. Heller, “Why you hear what you hear”. Vocal Tract Anatomy – Another View. Illustration from J. Sundberg , “The Acoustics of the Singing Voice”. Vocal Tract Anatomy – Another View.

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P105 Lecture #26 visuals

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  1. P105 Lecture #26 visuals 18 March 2013

  2. Anatomy of the Human Vocal Apparatus Illustration from E.J. Heller, “Why you hear what you hear”

  3. Vocal Tract Anatomy – Another View Illustration from J. Sundberg, “The Acoustics of the Singing Voice”

  4. Vocal Tract Anatomy – Another View • Sound wave production starts with the larynx

  5. Vocal Tract Anatomy – The Larynx View from above: Frontal view: Illustrations from E.J. Heller, “Why you hear what you hear”

  6. Bernoulli Effect • Discovered by Daniel Bernoulli in the mid 1700’s • Essentially a consequence of conservation of energy • Statement is that pressure and flow velocity are inversely related for incompressible (approx. constant density) fluid • Mathematically: p1 + ½ r1 v12 = p2+ ½ r2 v22 (where p = pressure, r = density, v = velocity)

  7. Function of the Vocal Folds • Can think of the vocal folds as a mass/spring system. Operates via Bernoulli Effect: expulsion of air from lungs  high flow through glottal opening • Low pressure • closes vocal • folds • flow stops • folds open • Repeat. Illustration from A.H. Benade, “Fundamentals of musical acoustics”

  8. Net Result: Periodic expulsion of “puffs” of air from lungs Top: volume velocity vs time for sound production at 125 Hz (male voice); Bottom: Power spectrum falls at 12 dB per octave Fourier Spectrum: From Rossing, Wheeler & Moore, The Science of Sound

  9. Sound Production Summary • Expulsion of air from lungs induces vibration of vocal folds (via the Bernoulli effect). • The vocal folds open and close with a frequency dictated by anatomy (geometry) plus applied tension (contraction of muscles connecting folds with cartilage). • Give rise to periodic puff emission with fundamentals around 100 Hz (male), 200 Hz (female), 300 Hz (children). These are just the vocal fold vibration frequencies. • Thus, the vocal fold vibration frequency sets the pitch • To understand harmonic structure of speech must also take into account the filtering effect of the vocal tract  next up.

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